1. Field of the invention
The present invention relates to a device for converting unbalanced analog electric signals into fully-differential signals for use in analog signal processing circuits.
2. Description of the Prior Art
Fully differential signals have been preferred in processing analog signals because of several advantages, including, above all, insensitivity to power supply noise and/or ground noise, digital signal noise, etc. This insensitivity is due to the fact that said noise is converted only in the common mode and are therefore not perceived in the differential signal.
In many cases, however, the input signal is unbalanced, or single-ended, and it is therefore necessary to initially convert it into a fully-differential (or balanced) signal. However, converters used so far for this purpose, as will be described in greater detail hereinafter, are vulnerable to noise from the power supply or from the circuit ground, which in many cases does not coincide with the signal ground. Other types of noise to which said converters are vulnerable are also digital signals, or of other types, which couple capacitively at high frequency. In any case, alterations of the signal are thus introduced from the beginning, and once said alterations are superimposed they can no longer be eliminated, even if the successive structure is balanced.